There's always training as a good excuse for running silent. Apart from that ... well, I'm not quite sure what these fast attack submarines are doing out and ab

There's always training as a good excuse for running silent. Apart from that ... well, I'm not quite sure what these fast attack submarines are doing out and about at all. Maybe looking for other subs in the area? But whatever they are doing probably benefits from being hard to detect. If you are comfortable with announcing yourself with active sonar and are not just on the way to somewhere else, why not just use a surface ship in the first place?